Electronic systems that include one or more Si-PICs can exhibit relatively higher bandwidth data transmission rates over longer distances with relatively fewer copper interconnections than is possible with electronic devices that include electronic integrated circuits (electronic IC dies). This is because the data is converted from an electrical signal to an optical one and then transmitted through waveguides and fibers.
An Si-PIC is an example of a semiconductor die that may be used in an electronic system, such as a switch or server. Si-PICs are capable of transmitting and receiving optical signals (e.g., pulses of light, etc.), which can be used to communicate data (e.g., large bundles of data, etc.). Generally, an Si-PIC is formed using silicon on insulator (SOI) technology. SOI technology requires use of a layered silicon-insulator-silicon substrate. More specifically, this layered substrate includes a first layer formed from silicon (Si), a second layer formed from an insulator material that is disposed on the first layer, and a third layer formed from Si that is disposed on the second layer. The silicon in the first and third layers may have different qualities or properties from each other. The second layer can be a buried oxide layer. The insulator material may be formed from silica (i.e., silicon dioxide) and/or any other suitable insulator. Generally, the third layer is known as an active layer that transports optical signals. This active layer is also where one or more photonic devices are patterned lithographically, epitaxially grown, and/or bonded or formed via other similar fabrication techniques.
As used herein, a photonic device includes any optical structure fabricated in or on an active layer of an Si-PIC that guides, generates, manipulates, or detects optical signals (e.g., pulses of light, etc.). Examples of photonic devices include one or more of the following: (i) a laser light source or amplifier formed from group III-V compound semiconductors (e.g., gallium arsenide (GaAs), aluminium gallium arsenide (AlGaAs), indium phosphide (InP), etc.); (ii) an optical modulator (e.g., a Mach-Zehnder interferometer (MZI), electro-absorption modulator (EAM) etc.); (iii) a micro-optical system (e.g., lenses, arrays of lenses, etc.); (iv) a photodetector; (v) an optical switch; and (vi) one or more silicon waveguides used to transport the optical signals to and from the other photonic devices.
Semiconductor packaging of Si-PICs, as used herein, refers to a range of techniques and technical competencies used to make optical, electrical, thermal, mechanical, and/or chemical connections between an Si-PIC and the outside world. An example of such an Si-PIC package that includes one or more of the following: (i) one or more Si-PICs; (ii) one or more electronic IC dies; (iii) a package substrate (e.g., a carrier substrate formed from silicon or other materials, organic build up materials, mold, etc.); (iv) interconnect structures (e.g., wire bonds, bumps, microbumps, pillars, etc.) for coupling the die(s) to the package substrate, another component in the package, or to another package; and (v) one or more thermal cooling components (e.g., at least one heat spreader, at least one heat sink, etc.).
One problem that can affect an Si-PIC package is unwanted stress that is introduced into the package by one or more processes used to the form the package. The stress may damage one or more photonic and/or electronic devices in the Si-PIC package. This damage can cause the photonic and/or electronic device(s) to malfunction, result in destruction of the photonic device(s), or cause degradation of the photonic performance or targeted wavelength and/or decay the lifetimes. For example, an Si-PIC package may include: (i) a laser light source soldered onto a heat spreader; and (ii) the heat spreader soldered onto a heat sink. This soldering process mechanically couples the laser to substrates with different coefficients of thermal expansion, which may introduce mechanical stress into the package that stresses or strains the laser light source as the laser operates and generates heat. The stress or strain applied to the laser may result in damaging the laser light source or shifting the wavelength of operation. Local stresses may negatively affect one or more photonic devices of an Si-PIC package causing changes in refractive indices of the one or more photonic devices. Such changes can result from temperature and/or pressure variations and each may affect the photonic device(s) performance.